Heater Box Buzzing
Crown vic make a buzzing sound on the highway when cruising at around 65MPH Solution for this problem: This problem is noticed by many others too ................... The whole dashboard vibrated sort of like the vehicle had a bee's nest hiding under the dash. Problem was not present when driving at slower speeds unless it was a windy day. Intensity and frequency of the noise varied depending on blower motor speed with the problem being eliminated if the climate controls were set to "off". Also, the noise was not present when the climate controls were set on "max ac", even if the blower was at high speed. Since both "max ac" and "off" close the door in the heater box that draws in outside air, my suspicious was that something was loose in path that the outside air comes in through. Had recently replaced the blower motor, so I knew the inside of the heater box was free of debris in the area that draws outside cabin air. Noticed